CH710701A1 - Preform for the production of a plastic container, production of the preform and produced from the preform plastic container and its production. - Google Patents

Abstract

It is a preform for producing a plastic container described in a stretch-blow molding process, which has an elongated, tube-like preform body which is closed at its one longitudinal end with a Preformboden and at its other longitudinal end has a Preformhals. The preform consists at least partially of polyethylene furanoate (PEF), which in the production of the preform has a viscosity of 0.75 dl / g to 0.9 dl / g measured by a measurement method according to ASTM D4603 and a water content of less than 50 ppm. Furthermore, a method for producing the preform, a stretch blow molding method for producing a container from the preform and a resulting container are described.

Description

The invention relates to a preform for producing a plastic container according to the preamble of claim 1. The invention also relates to the production of the preform and a plastic container produced from the preform and its production.

The usual in the past containers made of white or stained, glass or ceramic are increasingly being replaced by plastic containers. In particular for the packaging of fluid substances, for example beverages, flowable foodstuffs such as e.g. Ketchup, sugo, pesto, sauces, mustard, mayonnaise and the like, household products, care products, cosmetics, etc. are now mainly plastic containers used. The low weight and the lower costs certainly play a significant role in this substitution. The use of recyclable plastic materials, the use of bioplastics and the overall more favorable overall energy balance in their production also contribute to the consumer's acceptance of plastic containers, in particular plastic bottles.

A large number of plastic bottles and plastic containers used today are produced in a stretch blow molding process. In this method, first a so-called preform of usually elongated, tube-like shape is produced, which is closed at its one longitudinal end with a bottom and at the other longitudinal end has a neck portion with means for the positive fixing of a equipped with corresponding engagement means closure member. The means for the positive fixing of a closure part can be, for example, threaded sections or bayonet-type projections or corresponding recesses formed on the outer wall of the neck part. The production of the preform is usually done in an injection molding process. However, alternative production methods for preforms are also known, for example extrusion or extrusion blow molding. The production of the preforms can take place temporally and / or spatially separated from the subsequent stretch blow molding process. In an alternative method, the produced preform is further processed without intermediate cooling immediately after its production. For stretch blow molding, the preform is inserted into a mold cavity of a blow mold and expanded, in particular in the radial and axial direction, by means of a fluid, usually air, introduced with overpressure. In this case, the preform is additionally stretched in the axial direction with a retracting mandrel inserted through the neck opening of the preform. After the stretching / blowing process, the finished plastic container is removed from the blow mold.

The polyethylene terephthalate (PET) often used for the production of preforms and the plastic container made from them has only relatively low mechanical strength and only relatively poor barrier properties because of the usually more random arrangement of the molecules. In the subsequent stretch blow molding process, the PET is stretch-strengthened, which leads to an approximation and to a parallel alignment of the molecules. Intermolecular interactions of the molecules approximating each other and the molecular chains oriented parallel to one another lead to a significant improvement in the mechanical strengths of the plastics used.

The advantageous effects of the stretch hardening occur relatively late in the PET, which is usually used for the production of plastic containers. The resulting long stretching paths represent a not inconsiderable technical challenge in the radial and axial stretching. In order to achieve these high drawing rates in PET, the preform must have relatively small dimensions. Typically, the length of the preform is about 10 cm and has a diameter of about 2 cm. By contrast, the PET container produced from the preform by stretch blow molding is in many cases relatively large and, for example, has a length of about 24 cm and a width of about 7 cm in the case of a typical mineral water or soft drink bottle. Because of the high draw rates, the stretched PET container has only relatively small wall thicknesses, which has a negative effect on the barrier properties of the PET container, in particular with respect to oxygen and water.

The object of the present invention is therefore to provide a preform, which leads to the need for achieving the required mechanical strength yield rates in the stretch blow to a plastic container, which still has sufficiently large barrier properties to oxygen and water.

The solution to this problem consists in a preform having the features cited in claim 1, and in a method for producing the preform, which has the features cited in the independent method claim. The object is further achieved by a plastic container, which has been produced in a stretch blow molding from a preform according to the invention. Further developments and / or advantageous embodiments of the invention are the subject of the dependent claims.

The invention provides a preform for producing a plastic container is provided in a stretch blow molding, which has an elongated, tube-like preform body, which is closed at its one longitudinal end with a Preformboden and at its other longitudinal end has a preform neck. The preform consists at least partially of polyethylene furanoate (PEF), which in the production of the preform has a viscosity of 0.75 dl / g to 0.9 dl / g measured by a measuring method according to ASTM D4603, and a water content of less than 50 ppm having.

Polyethylene furanoate (PEF) has many similarities to its well-known polyethylene terephthalate (PET) in many aspects of its preparation and processability. Like PET, PEF achieves the required mechanical strength by stretch-stretching the preform during stretch blow molding to make a container. However, while PET has relatively poor barrier properties to oxygen, carbon dioxide or water because of the reduction in wall thickness as a result of increasing stretching, these disadvantages occur to a significantly lesser extent in the case of PEF.

PEF has barrier properties to oxygen, which are higher by about a factor of 6 to 10 than PET of the same wall thickness. The barrier properties to carbon dioxide are about a factor of 3 to 6 greater than for PET. Finally, PEF has barrier properties to water that are about twice as high as those of PET.

In order that the desired mechanical strength and the desired barrier properties of the later stretched from the preform produced preform container can be achieved, it is already ensured for the production of the preform that an optimal molecular length of the PEF chains is achieved. Therefore, for the production of the preforms, a viscosity of the PEF is set, which is 0.75 dl / g to 0.9 dl / g. The viscosity is determined by a method of measurement analogous to ASTM D4603. Although this standardized measuring method was developed for the determination of the viscosity of PET, it can be applied to PEF in an analogous form. The preform processed PEF has a water content of less than 50 ppm. For this, the PEF is dried before being processed. For example, the PEF is dried for 20 hours at 150 ° C and an air dew point below -30 ° C. The drying can be accelerated by increasing the temperature, but it is advisable to use a stirrer or a corresponding device to prevent sticking of the PEF material. In addition, even energy can be introduced by infrared or microwave radiation to further reduce the drying time. Finally, the drying of the PEF can also be done in a vacuum. The adjustment of the viscosity and the water content of the PEF prior to its processing to the preform ensure the maintenance of the molecular structure of the PEF and in particular its chain length. By drying the PEF, the hydrolytic degradation of the chains is reduced and chain scission of the PEF can be suppressed by hydrolysis, for example by injection molding of the PEF. The treatment of the PEF should be carried out as soon as possible to its further processing into a preform, otherwise oxidative degradation reactions damage the PEF. As a timely within the meaning of the present invention, a period of up to hours after the preparation of the PEF is considered. The PEF used for the production of the preform can have a linear chain structure or contain smaller or larger branches.

In an embodiment variant of the preform, the entire preform, including the preform neck, which is often not stretched in a subsequent stretch blow molding, consist of PEF.

In a further embodiment of the preform, the PEF used for its production may comprise 10% to 100% bio-based PEF. The use of bio-based PEF is worthwhile for ecological reasons, as exclusively renewable materials are used for the production of the PEF.

In one embodiment variant of the preform, the PEF used for its production may comprise up to 100% regenerated material. As a result of the manufacturing process used and the temperatures used for the drying and further processing of the PEF, any impurities with other substances, in particular with foreign polymers, play a subordinate role. Therefore, preforms containing regenerated material and the containers made from them can come into direct contact with the contents without any restrictions.

A further embodiment of the preform may provide that the PEF is foamed physically or chemically. The PEF may have a degree of foaming of 10% to 30%. The foaming of the PEF can take place within the mold cavity or even already in a melt reservoir before the actual injection into the injection mold for the production of the preform.

In one embodiment variant of the preform, the PEF used for its production may be produced in a solid state polycondensation (SSD) process or in a melt to resin (MTR) process. For the preparation of a catalyst is selected, which comes from the group consisting of alkali metals, alkaline earth metals, transition metals or metals of the Periodic Table of the Elements. Typically, the catalyst is used as a salt, oxide, glycolate or complex of these elements.

In a further embodiment of the preform, the PEF may comprise up to 20 percent by weight impurities. In the context of the present invention, foreign substances, dyes, fillers, stabilizing additives, such as, for example, are used as foreign substances. Glass fibers or glass spheres or mixtures thereof, additives or foreign polymers considered.

A variant of the preform may provide that the PEF used for its production is mixed with other plastics. These other plastics may be selected from the group consisting of PET, polyester, polyamide, polycarbonate, polyolefins, silicones, their copolymers and mixtures of plastics.

So that it does not come to a hydrolytic splitting of the chain lengths, the PEF can be dried, for example, at a drying temperature of 100 ° C to 160 ° C. Alternatively, the PEF can be dried at temperatures of greater than 160 ° C up to 220 ° C when using special stirring mechanisms, which avoid sticking of the PEF and loosen any adhesions. From a temperature of 220 ° C, despite agitator and any special coatings of the granules a normal fluid-driven drying process is no longer possible, as the PEF begins to melt. The drying process of the PEF can be assisted by the supply of energy in the form of microwave radiation and can even take place under vacuum.

For the production of the preform, the PEF can be heated to a processing temperature greater than the melting temperature but less than 290 ° C, measured at the outlet of an extruder for conveying the PEF to the manufacturing device for the preform. Typically, the PEF is heated to temperatures between 220 ° C and 290 ° C. These temperatures apply to the further processing of the PEF by injection molding, by extrusion blow molding or by flow casting.

In one embodiment of the invention, the preform can be produced in an injection molding in a mold cavity with a hot runner system with a needle valve from 3.9 mm to 6.1 mm. Preferably, the diameter of the needle valve is 4.5 mm to 5.5 mm. In such hot runner systems with larger valve gate, relatively tough PEF melts with relatively high viscosity can be injected into the mold. This allows the injection molding process to be carried out at lower temperatures. This leads to lower residence times under high temperature of the PEF melt in the injection molding plant. As a result, thermal degradation of the PEF molecule chains can be counteracted. Long molecular chains of the PEF are aimed at favoring the strain hardening.

In a further embodiment variant, a thermally oxidative degradation of the PEF in the extruder can be suppressed by displacing the oxygen, for example by nitrogen at the inlet of the extruder. The lack of oxygen can reduce oxidative degradation processes, reduce yellowing, and increase the time to co-prime PEF with other polyesters. Copolymerization may be advantageous for incorporating other esters into the PEF molecular chains, thus modifying the properties of the PEF to the desired extent. For example, copolymerization of the PEF with PET, PBT, PEN, PLA may be of interest.

In one embodiment of the method for producing the preform by injection molding, the PEF can be introduced into the injection mold at a rate of 11 g / sec to 30 g / sec. The fast injection molding process can lead to a certain material orientation, in particular in the case of thin-walled preforms, which in turn is advantageous in the case of stretch hardening in the subsequent stretch blow molding process, since the molecular chains are already preoriented

Another variant of the method may provide that PEF is introduced with a melt pressure of 700 bar to 3000 bar in the mold cavity of the injection mold. This pressure is usually measured at the screw tip of the feed extruder or upstream in the injection unit melt storage. This allows the processing of viscous PEF melts, which can be beneficial to the thermal degradation of molecular chains.

In an alternative manufacturing variant, the preform can be produced in an extrusion blow molding process. The extrusion blow molding method allows higher degrees of freedom with regard to the shaping of the preform. In particular, eliminates an injection core, which must be removed from the mold. As a result, the preform may also have undercuts in its interior. It should be noted at this point that the preform can in principle also be formed during injection molding with undercuts in its interior. However, this requires a more complex equipment, for example in the form of a spreading core or the like. However, this increases the unit costs and often also extends the cycle times.

A variant of the manufacturing process of the preform in the extrusion blown process can provide that the PEF is introduced at an extrusion pressure of 100 bar to 300 bar in an extrusion channel of an extruder head. The extrusion pressure refers to the pressure of the PEF melt immediately before entering the extrusion channel of the extrusion head. With the selected pressure, even viscous PEF melts can be processed by extrusion blow molding. The resulting lower heating of the PEF melt has a positive effect on the prevention of thermal degradation of the PEF molecule chains.

In a variant of the method, the PEF can be extruded through a Ringpaltdüse with a width of 1 mm to 4 mm as a tube before a portion of the extruded tube is inflated in a mold cavity of a blow mold by a medium blown with overpressure medium to the preform.

In a further process variant for the production of the preform, this can also be produced in a flow molding process within a mold cavity.

The preform produced by injection molding, by extrusion blow molding or by flow molding is cooled after its production. For this purpose, the prepared preform can be cooled in a first step still within the mold cavity to a temperature which is 30 ° C to 110 ° C below the melting temperature, but above the glass transition temperature of the PEF.

In a variant of the method, the preform produced can be cooled after its removal from the mold cavity in a cooling sleeve to a temperature of its outer wall of 40 ° C to 70 ° C before it is removed for further processing or for intermediate storage from the cooling sleeve. The cooling sleeve ensures the most even and gentle cooling of the preform. A sticking together of the preforms or damage to the Preformaussenwandung can be avoided.

A plastic container according to the invention with a container body which is closed with a container bottom, and with a container neck to the container body neck with a pouring opening is characterized in that it is produced in a stretch blow molding from a preform, which is made according to the invention , is made. The plastic container consists at least in part, preferably entirely, of stretch-hardened PEF. With regard to its processability and strain hardening, PEF has great similarities to the well-known PET. However, while PET has relatively poor oxygen barrier properties due to wall thickness reduction due to increasing draw. Having carbon dioxide or water, these disadvantages occur in PEF to a much lesser extent. PEF has barrier properties to oxygen, which are higher by about a factor of 6 to 10 than in PET of the same wall thickness. The barrier properties to carbon dioxide are about a factor of 3 to 6 greater than for PET. Finally, PEF has barrier properties to water that are about twice as high as those of PET.

The stretched from a PEF preform plastic container reaches the required mechanical strength already at a measured over the surface contour draw ratio compared to the preform of 100% to 1000%. This is achieved by the fact that the PEF molecule chains already have a certain preorientation as a result of the special production process of the preform. In the stretch blow-molding process, therefore, a sufficient approximation and a sufficient parallel orientation of the PEF molecule chains occur relatively early. The improved mechanical strengths are then a consequence of the intermolecular interactions of the approximated and aligned parallel molecular chains.

Achieving the required strain hardening can be expressed in a rotationally symmetrical container body having plastic container in that it has halfway up its container body over the circumference of a wall thickness distribution that does not deviate more than +/- 10% from a target wall thickness.

In a plastic container with an oval container body with a depth to width ratio of up to 1: 2, the achievement of the desired Streckverfestigung may express that this halfway up the container body over the circumference has a wall thickness distribution that no more than +/- 25% deviates from a target wall thickness.

In a plastic container having a so-called flat container body, the ratio of depth to width is greater than 1: 2 but less than 1:10, the achievement of the desired Streckverfestigung can ußern in that he halfway up the container body has a wall thickness distribution over the circumference, which deviates no more than +/- 50% from a desired wall thickness.

As a further indication of the achievement of the desired strain hardening can be used that the PEF plastic container when filled with a CO2-containing contents and a CO2 content at 23 ° C from 4 to 10 g / 1 at a temperature increase to 38 ° C. within 24 hours only suffers an increase in volume that is less than 10%.

In the filled state with an inert gas, in particular nitrogen, filled PEF plastic containers, which leads at 23 ° C to an internal pressure of 0.2 bar to 2 bar, the achievement of the desired Streckverfestigung can be controlled that the plastic container at Increasing the temperature to 38 ° C within 24 hours only suffers an increase in volume that is less than 10%.

A sufficiently stretch-strengthened plastic container, stretch-blown as a pressure vessel from a preform consisting at least in part of PEF, may have a pressure resistance of at least 100% above the filling pressure at 23 ° C. As a result, it is generally ensured that the plastic container does not fail when used properly, neither during filling nor during later handling by the consumer.

For producing a plastic container made of a preform according to the invention in a stretch blow molding process, the preform is after the heating of his Preformkörpers to a processing temperature which is 5 ° C to 25 ° C above the glass transition temperature of the PEF, inserted into a mold cavity of a blow mold and through inflated blown with an overpressure blowing medium and thereby axially stretched by means of a stretching mandrel. Thereafter, the biaxially stretched plastic container is removed from the blow mold.

For the stretch blow molding of the preform, it is important that the preform has absorbed as little water as possible and as possible no other molecules, such as waxes, oils, etc., as they are often used for color masterbatches contains. As a result, slippage of the molecular chains can be prevented even at low rates of stretching and stretching rates. The heating of the preform thus also serves for drying and evaporation of the mentioned foreign substances. On the other hand, the stretch blow process of the preform is performed as cold as possible. The colder the preform used in the mold cavity, the sooner the stretch hardening of the PEF material begins. At the selected temperature of the preform, both requirements can be satisfactorily met. The temperature refers to both the outer wall and on the inner wall of the preform and is set to 5 ° C to 25 ° C above the glass transition temperature. Ideally, the temperature of the preform is between 105 ° C and 145 ° C.

In a variant of the method, the axial stretching of the preform can take place with a stretching mandrel speed of 0.5 m / s to 3 m / s. The axial feed rate of the stretching mandrel takes place so fast that the front end of the stretching mandrel is always in contact with the blister formed from the preform and moves as fast as the bladder during the expansion of the bladder by the pressurized fluid during the blowing process.

The blowing medium, usually air, can be introduced in a further process variant in two stages. In a first stage, the blowing medium is introduced into the mold cavity at a first flow rate of 0.02 l / s to 51 / s. At the same time, the stretching mandrel is advanced axially so fast that it does not detach from the bubble formed by the blown-in blowing medium from the preform. The feed rate of the stretching mandrel thus corresponds to the longitudinal extent of the blister formed from the preform. As soon as the bubble rests against the bottom of the mold cavity, in a second stage the blowing medium is then blown in at a second flow rate of 0.51 / s to 101 / s until the bubble formed from the preform rests against the inner walls of the blow mold bounding the mold cavity.

The pressure with which the blowing medium is blown into the preform can be 5 bar to 50 bar.

For a uniformly fast stretching of the PEF preform, it is important that its expansion is not hindered by a back pressure, in order to give the PEF molecule chains no time for slipping, flowing or unthreading. This back pressure can be avoided by venting the mold cavity of the blow mold at a flow rate of 0.021 / s to 51 / s. For this purpose, corresponding vent holes may be provided in the blow mold.

Stretch blown plastic containers made of PEF preforms can be used like PET containers. At comparable wall thicknesses, the PEF has significantly better barrier properties compared to PET with respect to oxygen, carbon dioxide and water. Plastic containers made of PEF can therefore be produced in many cases without additional layers of foreign polymers or on additives, for example to increase the oxygen barrier. This, the fact that PEF can be produced entirely from biological and renewable raw materials, and the full recyclability increase the environmental benefits of PEF containers over comparable containers, for example made of PET.

Claims (36)

1. preform for producing a plastic container in a stretch-blow molding process with an elongated, tubular preform body (2) which is closed at its one longitudinal end with a Preformboden (3) and at its other longitudinal end a Preformhals (4), characterized in that Preform at least partially made of polyethylene furanoate (PEF), which in the production of the preform has a viscosity of 0.75 dl / g to 0.9 dl / g measured by a measurement method according to ASTM D4603 and a water content of less than 50 ppm. 2. Preform according to claim 1, characterized in that the PEF comprises 10% to 100% bio-based PEF. 3. Preform according to claim 1 or 2, characterized in that the PEF comprises up to 100% regenerated material. 4. Preform according to one of claims 1 to 3, characterized in that the PEF is foamed physically or chemically and has a foaming degree of 10% to 30%. 5. Preform according to one of the preceding claims, characterized in that the PEF is prepared in a solid state polycondensation (SSD) process or in a melt to resin (MTR) process, with a catalyst selected from the group consisting of alkali metals, Alkaline earth metals, transition metals or metals of the Periodic Table of the Elements, typically as salt, oxide or complex of these elements. 6. Preform according to one of the preceding claims, characterized in that the PEF comprises up to 20 weight percent foreign substances. 7. Preform according to claim 6, characterized in that the PEF dyes, stabilizing additives such. Glass fibers or glass spheres or mixtures thereof, additives or foreign polymers. 8. preform according to one of the preceding claims, characterized in that the PEF is mixed with other plastics. 9. preform according to claim 8, characterized in that the further plastics from the group consisting of PET, polyester, polyamide, polycarbonate, polyolefins, silicones, their copolymers and mixtures of the plastics are selected. 10. A process for producing a preform according to claim 1, characterized in that the PEF is dried at a drying temperature which is 100 ° C to 160 ° C. 11. A process for producing a preform according to claim 1, characterized in that the PEF is dried at a temperature of greater than 160 ° C up to 220 ° C and agitated during the drying process with a stirrer. 12. The method according to claim 10 or 11, characterized in that the drying process of the PET is supported by the supply of energy in the form of microwave radiation. 13. The method according to any one of claims 10 to 12, characterized in that the drying of the PEF takes place under vacuum or an oxygen-displacing non-oxidative gas. 14. The method according to any one of claims 10 to 13, characterized in that the PEF for the production of the preform to a processing temperature greater than the melting temperature but less than 290 ° C, measured at the outlet of an extruder for conveying the PEF to the manufacturing device for the preform , is heated. 15. The method according to any one of claims 10 to 14, characterized in that the preform in an injection molding in a mold cavity with a hot runner system with a needle valve of 3.9 mm to 6.1 mm, preferably 4.5 mm to 5.5 mm , will be produced. 16. The method according to claim 15, characterized in that the PEF is introduced at a rate of 11 g / sec to 30 g / sec in an injection mold. 17. The method according to claim 15 or 16, characterized in that the PEF is introduced with a melt pressure of 700 bar to 3000 bar in an injection mold. 18. The method according to any one of claims 10 to 14, characterized in that the preform is produced in an extrusion blow molding process. 19. The method according to claim 18, characterized in that the PEF is introduced with an extrusion pressure of 100 bar to 300 bar in an extrusion channel of an extruder head. 20. The method according to claim 18 or 19, characterized in that the PEF is extruded through a Ringpaltdüse with a width of 1 mm to 4 mm as a tube, before a portion of the extruded tube in a mold cavity of a blow mold by a pressurized medium to the Preform is inflated. 21. The method according to any one of claims 10 to 14, characterized in that the preform is produced in a flow molding process within a mold cavity. 22. The method according to any one of claims 10 to 21, characterized in that the preform produced is cooled within the mold cavity to a temperature which is 30 ° C to 110 ° C below the melting temperature, however, above the glass transition temperature of the PEF. 23. The method according to claim 22, characterized in that the prepared preform is cooled after its removal from the mold cavity in a cooling sleeve to a temperature of its outer wall of 40 ° C to 70 ° C before it is removed for further processing or for intermediate storage from the cooling sleeve becomes. 24. Plastic container with a container body which is closed with a container bottom, and with a subsequent to the container body container neck with a pouring opening, characterized in that it is manufactured in a stretch blow molding from a preform, which is prepared according to one of claims 10 to 23 is. 25. Plastic container according to claim 24, characterized in that it has a relation to the preform measured over the surface contour stretch ratio of 100% to 1000%. 26. Plastic container according to claim 24 or 25, characterized in that it has half a height of its container body a rotationally symmetrical cross-section and in this area over the circumference has a wall thickness distribution which does not deviate more than +/- 10% from a nominal wall thickness , 27. Plastic container according to claim 24 or 25, characterized in that it has an oval container body with a depth to width ratio of up to 1: 2 and halfway up the container body over the circumference has a wall thickness distribution which does not exceed +/- 25% deviates from a target wall thickness. 28. Plastic container according to claim 24 or 25, characterized in that it comprises a flat container body whose ratio of depth to width is greater than 1: 2 but less than 1:10, and that it is halfway up the container body over the circumference Wall thickness distribution that does not deviate more than +/- 50% from a target wall thickness. 29. Plastic container according to one of claims 24 to 28, characterized in that it at filling with a CO2-containing contents and a CO2 content at 23 ° C of 4 to 10 g / 1 at a temperature increase to 38 ° C within 24 hours a Volume increase less than 10%. 30. Plastic container according to one of claims 24 to 28, characterized in that it in the filled state and at an internal pressure of 0.2 bar to 2 bar of an inert gas, in particular nitrogen, at 23 ° C with increasing the temperature to 38 ° C within from 24 hours undergoes an increase in volume that is less than 10%. 31. Plastic container according to one of claims 24 to 30, characterized in that it is designed as a pressure vessel and has a pressure resistance of at least 100% above the filling pressure at 23 ° C. 32. A method for producing a plastic container according to any one of claims 24 to 31, characterized in that the preform after heating its Preformkörpers to a processing temperature which is 5 ° C to 25 ° C above the glass transition temperature of the PEF, in a mold cavity of a blow mold used and inflated by a blown with excess pressure blowing medium, thereby axially stretched by means of a stretching mandrel and then removed from the blow mold. 33. The method according to claim 32, characterized in that the axial stretching of the preform takes place at a stretching mandrel speed of 0.5 m / s to 3 m / s. 34. The method according to claim 33, characterized in that the blowing medium is introduced in a first stage at a first flow rate of 0.021 / s to 51 / sec in the mold cavity and then in a second stage with a second flow rate of 0.051 / s to 51 / s is blown. 35. The method according to claim 34, characterized in that the mold cavity of the blow mold is vented at a flow rate of 0.021 / s to 51 / s. 36. The method according to any one of claims 32 to 35, characterized in that the blowing medium is introduced at a pressure of 5 bar to 50 bar in the preform.